The subject matter of U.S. Pat. No. 5,709,784 is incorporated by reference herein.
The present invention is directed on a tool with a tool body and a wear resistant layer system, wherein the layer system comprises at least one layer of MeX, wherein
Me comprises titanium and aluminum, PA1 X is at least one of nitrogen and of carbon. PA1 The term Q.sub.I is defined as the ratio of the diffraction intensities I(200) to I(111), assigned respectively to the (200) and (111) plains in the X ray diffraction of a material using the .theta.-2.theta. method. Thus, there is valid Q.sub.I =I(200)/I(111). The intensity values were measured with the following equipment and with the following settings: PA1 Power: PA1 Operating voltage: 30 kV PA1 Operating current: 25 mA PA1 Aperture Diaphragms: PA1 Diaphragm position I: 1.degree. PA1 Diaphragm position II: 0.1.degree. PA1 Detector Diaphragm: Soller slit PA1 Time constant: 4 s PA1 2.theta. angular speed: 0.05.degree./min PA1 Radiation: Cu-K.alpha.(0.15406 nm) PA1 We understand by "tool body" the uncoated tool. PA1 We understand under "hard material" a material with which tools which are mechanically and thermally highly loaded in operation are coated for wear resistance. Preferred examples of such materials are referred to below as MeX materials. PA1 1 GPa.ltoreq..sigma..ltoreq.4 GPa, thereby most preferably PA1 1.5 GPa.ltoreq..sigma..ltoreq.2.5 GPa. PA1 70 at %.gtoreq.x.gtoreq.40 at %, thereby in a further PA1 65 at %.gtoreq.x.gtoreq.55 at %. PA1 30 at %.ltoreq.y.ltoreq.60 at %, in a further preferred embodiment even to be PA1 35 at %.ltoreq.y.ltoreq.45 at %.
Definition
Siemens Diffractometer D500
When we refer to "measured according to MS" we refer to this equipment and to these settings. Thereby, all quantitative results for Q.sub.I and I throughout this application have been measured by MS.
It is well-known in the tool-protecting art to provide wear resistant layer systems which comprise at least one layer of a hard material, as defined by MeX.
The present invention has the object of significantly improving the lifetime of such tools. This is resolved by selecting for said at least one layer a Q.sub.I value, for which there is valid EQU Q.sub.I .gtoreq.1
and wherein the tool body is made of high speed steel (HSS) or of cemented carbide, whereby said tool is not a solid carbide end mill or a solid carbide ball nose mill. Further, the value of I(200) is higher by a factor of at least 20 than the intensity noise average level as measured according to MS.
According to the present invention it has been recognised that the Q.sub.I values as specified lead to an astonishingly high improvement of wear resistance, and thus of lifetime of a tool, if such a tool is of the kind as specified.
Up to now, application of a wear resistant layer systems of MeX hard material was done irrespective of interaction between tool body material and the mechanical and thermal load the tool is subjected to in operation. The present invention thus resides on the fact that it has been recognised that an astonishing improvement of wear resistance is realised when selectively combining the specified Q.sub.I value with the specified kind of tools, thereby realising a value of I(200) higher by a factor of at least 20 than the average noise intensity level, both measured with MS.
With respect to inventively coating cemented carbide tool bodies, it has further been recognised that a significant improvement in lifetime is reached if such cemented carbide tools are inserts, drills or gear cutting tools, as e.g. hobs or shaper cutters, whereby the improvement is especially pronounced for such inserts or drills.
The inventively reached improvement is even increased if Q.sub.I is selected to be at least 2, and an even further improvement is realised by selecting Q.sub.I to be at least 5. The largest improvement are reached if Q.sub.I is at least 10. It must be stated that Q.sub.I may increase towards infinite, if the layer material is realised with a unique crystal orientation according to a diffraction intensity I(200) at a vanishing diffraction intensity I(111). Therefore, there is not set any upper limit for Q.sub.I which is only set by practicability.
As is known to the skilled artisan, there exists a correlation between hardness of a layer and stress therein. The higher the stress, the higher the hardness.
Nevertheless, with rising stress, the adhesion to the tool body tends to diminish. For the tool according to the present invention, a high adhesion is rather more important than the highest possible hardness. Therefore, the stress in the MeX layer is advantageously selected rather at the lower end of the stress range given below.
These considerations limit in practice the Q.sub.I value exploitable.
In a preferred embodiment of the inventive tool, the MeX material of the tool is titanium aluminum nitride, titanium aluminum carbonitride or titanium aluminum boron nitride, whereby the two materials first mentioned are today preferred over titanium aluminum boron nitride.
In a further form of realisation of the inventive tool, Me of the layer material MeX may additionally comprise at least one of the elements boron, zirconium, hafnium, yttrium, silicon, tungsten, chromium, whereby, out of this group, it is preferred to use yttrium and/or silicon and/or boron. Such additional element to titanium and aluminum is introduced in the layer material, preferably with a content i, for which there is valid EQU 0.05 at. %.ltoreq.i.ltoreq.60 at. %,
taken Me as 100 at %.
A still further improvement in all different embodiments of the at least one MeX layer is reached by introducing an additional layer of titanium nitride between the MeX layer and the tool body with a thickness d, for which there is valid
0.05 .mu.m.ltoreq.d.ltoreq.5 .mu.m.
In view of the general object of the present invention, which is to propose the inventive tool to be manufacturable at lowest possible costs and thus most economically, there is further proposed that the tool has only one MeX material layer and the additional layer which is deposited between the MeX layer and the tool body.
Further, the stress .sigma. in the MeX is preferably selected to be
within the range
The content x of titanium in the Me component of the MeX layer is preferably selected to be
preferred embodiment within the range
On the other hand, the content y of aluminum in the Me component of the MeX material is preferably selected to be
In a still further preferred embodiment, both these ranges, i.e. with respect to titanium and with respect to aluminum are fulfilled.
The deposition, especially of the MeX layer, may be done by any known vacuum deposition technique, especially by a reactive PVD coating technique, as e.g. reactive cathodic arc evaporation or reactive sputtering. By appropriately controlling the process parameters, which influence the growth of the coating, the inventively exploited Q.sub.I range is realised.
To achieve excellent and reproducible adhesion of the layers to the tool body a plasma etching technology was used, as a preparatory step, based on an Argon plasma as described in U.S. Pat. No. 5,709,784.